The present invention relates to a structure for enhanced cooling of a dynamoelectric machine rotor by intercepting and redirecting a circulating coolant flow in a cavity.
In large dynamoelectric machines, such as a turbo-generator, the rotor consists of machined slots along its length in which copper coils are placed. The portions of these coils which extend outside the rotor body are called endwindings. In the endwinding region of a rotor, coils are held tightly by spaceblocks, which are further classified as space, spacer and wedge blocks, depending on their location.
The power output rating of dynamoelectric machines is often limited by the ability to provide additional current through the rotor field winding because of temperature limitations imposed on the electrical conductor insulation. Therefore, effective cooling of the rotor winding contributes directly to the output capability of the machine. This is especially true of the rotor endwindings, where direct, forced cooling is difficult and expensive due to the typical construction of these machines. As prevailing market trends require higher efficiency and higher reliability in lower cost, higher-power density generators, cooling the rotor endwindings becomes a limiting factor. In order to cool the endwindings and coils, a circulating coolant flow is passed through the cavities between spaceblocks and coils, and enters the grooves in coils, which start from these cavities and discharge into a chimney.
U.S. Pat. No. 6,465,917 describes a method for augmenting heat transfer by providing a spaceblock having at least one flow deflector structure provided on a cavity facing surface for intercepting and redirecting circulating coolant flow towards a central region of the respective cavity deflector structure increasing the flow velocity of the large single flow circulation cell by introducing additional cooling flow directly into, and in the same direction as, the naturally occurring flow cell. This approach is shown in FIGS. 4 and 5 of the present application. While this method increases the heat transfer in the cavity by augmenting the strength of the circulation cell, the center region of the cavity may still be left with low velocity and therefore low heat transfer.